Functions such as ST_GeomFromText()
that accept WKT geometry collection arguments understand both
OpenGIS 'GEOMETRYCOLLECTION EMPTY' standard
syntax and MySQL 'GEOMETRYCOLLECTION()'
nonstandard syntax. Another way to produce an empty geometry
collection is by calling
GeometryCollection() with no
arguments. Functions such as
ST_AsWKT()
that produce WKT values produce 'GEOMETRYCOLLECTION
EMPTY' standard syntax:

Unless otherwise specified, functions in this section handle their
arguments as follows:

If any argument is NULL, the return value
is NULL.

If any geometry argument is not a syntactically well-formed
geometry, an
ER_GIS_INVALID_DATA error
occurs.

If any geometry argument is in an undefined spatial reference
system, the axes are output in the order they appear in the
geometry and an
ER_WARN_SRS_NOT_FOUND_AXIS_ORDER
warning occurs.

By default, geographic coordinates (latitude, longitude) are
interpreted as in the order specified by the spatial reference
system of geometry arguments. An optional
options argument may be given to
override the default axis order. options
consists of a list of comma-separated
key=value.
The only permitted key value is
axis-order, with permitted values of
lat-long, long-lat and
srid-defined (the default).

If the options argument is
NULL, the return value is
NULL. If the
options argument is invalid, an
error occurs to indicate why.

Otherwise, the return value is non-NULL.

These functions are available for format conversions or coordinate
swapping:

Converts a value in internal geometry format to its WKB
representation and returns the binary result.

The function return value has geographic coordinates
(latitude, longitude) in the order specified by the spatial
reference system that applies to the geometry argument. An
optional options argument may be
given to override the default axis order.

Converts a value in internal geometry format to its WKT
representation and returns the string result.

The function return value has geographic coordinates
(latitude, longitude) in the order specified by the spatial
reference system that applies to the geometry argument. An
optional options argument may be
given to override the default axis order.